The present invention relates to an endoscope apparatus capable of calculating biological function information, such as the oxygen saturation of a biological mucosa, with high precision while reducing an influence of the motion of a subject.
In diagnostic imaging using an endoscope, detailed observation or detailed diagnosis is performed in which each site in a wide range of a body cavity is screened by normal light observation using normal white illumination light to find a site suspected of abnormality, the site suspected of abnormality is then observed/examined accurately, precisely, and in detail, and cancer in the body cavity, particularly, the focus site of early-stage cancer, a lesion site, or an abnormal site, such as a hemorrhage, is diagnosed.
In detailed observation/diagnosis (hereinafter, collectively called diagnosis) using the endoscope, when the site suspected of abnormality found in screening is approached, it is necessary to accurately determine whether or not the relevant site is an abnormal site, such as cancer. For this reason, as diagnostic images, it is necessary to observe and diagnose the relevant site in a close contact or enlarged state, or to perceive biological changes in a plurality of features of the relevant site, and there is demand for obtaining a plurality of images using light having various wavelengths.
For this reason, detailed diagnosis is generally performed by special light observation of an enlarged target site. As special light observation, the following observation is performed: narrowband light observation in which light (narrowband light) in a narrow wavelength band having a specific center wavelength is irradiated onto the mucosal tissue of the biological object using the fact that the invasion depth of light in the depth direction with respect to the biological tissue depends on the wavelength of light, and tissue information at a desired depth of a biological tissue, particularly, form information of a blood vessel at a predetermined depth (surface layer blood vessel (blue: B), intermediate layer blood vessel (green: G), deep layer blood vessel (red: R), or the like) are obtained to diagnose the presence/absence of a focus, such as a cancer tissue; narrowband light observation in which narrowband light in the B region is irradiated onto a biological tissue using the absorbance of hemoglobin and the oxygen saturation in the blood is measured; infrared light observation in which near-infrared light is irradiated onto a biological tissue using the absorbance of hemoglobin or the absorbance of ICG (indocyanine green) to be bound to protein and the oxygen saturation in the blood is measured to image a blood vessel; or fluorescent observation in which the presence/absence of a focus, such as cancer cells, is determined using autogenous fluorescence generated from a biological tissue, onto which excitation light in a specific narrow wavelength band is irradiated or fluorescence generated from a fluorescent medication dispersed in a specific focus, such as cancer cells, in a biological tissue.
For example, Patent Document 1 describes an endoscope system which has three observation modes including a normal light observation mode in which a reflected light image is presented, a screening fluorescent observation mode (first fluorescent observation mode) in which a fluorescence intensity image is presented, and unmixing fluorescent observation mode (second fluorescent observation mode) in which the concentration distribution of a fluorescent medication obtained by computation from a fluorescence intensity image is presented, and can select a suitable observation mode by a mode selector.
In this endoscope system, a white light source, such as a xenon lamp, a light source for illumination light constituted by a switching RGB color filter, and two excitation light sources constituted by semiconductor lasers which emit excitation light having different wavelengths with the peak wavelengths of 680 nm and 700 nm are used as light sources. While the insertion portion at the tip of the endoscope is inserted into a body cavity and then reaches an observation site, imaging is done in the normal light observation mode using the light source for illumination light, that is, normal screening is performed. In this mode, the two excitation light sources are turned off. If the insertion portion at the tip of the endoscope reaches the observation site, the observation mode is switched to the screening fluorescent observation mode, such that the observation-target site is cleaned and two fluorescent probes are dispersed.
In the screening fluorescent observation mode, the light source for illumination light and one excitation light source are used. When the light source for illumination light is turned on, only B illumination light is irradiated onto the observation site, and imaged as a reflected light image (B) by an image pickup device. When the excitation light source is turned on, two kinds of fluorescence which are generated when the two fluorescent probes dispersed in the observation site are excited by emitted excitation light are imaged as fluorescent images by an image pickup device including an excitation light cut filter, and are displayed on a display unit as an image in which a fluorescent image and a reflected light image overlay each other. If fluorescence is generated, the observation mode is switched to the unmixing observation mode. When fluorescence is not generated, the observation mode is switched to the normal observation mode, moving to the next observation site.
In the unmixing observation mode, the light source for illumination light and the two excitation light sources are used. In the same manner as described above, two kinds of fluorescent images in which a reflected light image and two kinds of fluorescence are color-mixed are acquired, concentration information of the fluorescent probes is calculated from the two kinds of fluorescent images, and overlaid on the reflected light image to be displayed on the display unit. It is possible to determine the presence/absence of a cancer cell on the basis of the concentration information with the two kinds of fluorescence.
[Patent Document 1] JP 2008-161550 A